<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div>hello</div>
  <script>
    let div = document.querySelector('div')

    div.style.color = 'red';
    div.style.color = 'blue'

    // JS出现的那个年龄，计算机的配置非常低
  </script>
</body>

</html>